The present invention relates to a drive chain and more particularly but not exclusively, to a roller-type chain.
In many chain drive applications links of the chain extend with use and the chain can become slack particularly during the period of initial use when components of the chain are "worn in". In such circumstances it is necessary to remove links of the chain so as to reduce excessive slack. Moreover, it is sometimes necessary to detach the chain from the drive assembly in which it is used in order that maintenance work on the drive assembly can be performed. Furthermore, in certain applications it is desirable for long lengths of chain to be separated into manageable lengths for transport and delivery purposes. For example, leisure park rides such as roller-coasters or the like generally use continuous loop drive chains to transport a vehicle in at least part of its ride. In the case of travelling fairs rides of this type have to be designed so that they are easily transportable. Other permanent amusement or leisure parks may have temporary "guest" or on-loan amusement rides which are only present for a limited period of time before they are dismantled and transported elsewhere.
Conventional roller chains comprise a sequence of links interconnected by pins which are interference fits in holes provided in the chain links. Each pin is located in a fixed bush which supports a rotatable cylindrical roller. In order to detach a drive chain from its assembly or to remove links it is necessary to remove one or more pins. Removal of the pin from an interference fit connection with the respective link causes wear and damage to the holes in the link. This is a particular problem with chains having cranked links as a new replacement link cannot be inserted without causing damage since this would involve removing the next pin in the chain thereby causing damage to the adjacent link in the chain.
In order to solve this problem it is known to use slip-fit pins in chains where frequent disconnection is required. A slip-fit connection between each pin and the corresponding hole in each link plate enables the chain to be disconnected many times without damaging the chain. However, the use of slip-fit connections reduces the fatigue resistance of the chain as a whole since the fatigue performance of the connection does not match that of the rest of the chain and is impaired since it is dependent on an interference fit between the pin and link plate in order to provide pre-stressing in the link plate hole. Pre-stressing is known to improve significantly fatigue resistance of the connection.
It is an object of the present invention to obviate or mitigate the aforesaid disadvantages.